This invention relates to a unique discharge valve for scroll compressors which provides a better seal, and is better adapted to withstand the operation of a scroll compressor than the prior art valves.
Scroll compressors have become widely utilized in refrigerant compression applications. Since scroll compressors have greater efficiency than many other types of compressors, they are attractive for many applications. However, scroll compressors also present many design challenges.
Scroll compressors typically utilize two interfitting scroll members. Each member has a base with a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the wraps orbits relative to the other to cause the compression chambers to change in volume, thus compressing entrapped refrigerant.
One challenge with scroll compressor operation occurs at shutdown. At shutdown of a scroll compressor, the volume of compressed gas trapped between the wraps and the relatively large volume of compressed gas contained within the discharge plenum, discharge lines and condenser can drive the orbiting scroll in a reverse direction. This reverse rotation may continue until pressures on the high pressure side of the system equalize with pressures on the low side of the system. Such prolonged reverse rotation is undesirable.
To address this challenge, scroll compressors have been provided with a discharge valve. The discharge valve is typically not a spring biased valve, but instead is free to pivot between an open and closed position. The discharge valve is open when the compressor is compressing refrigerant, but quickly moves to a closed position upon shutdown. The valve thus blocks flow of compressed refrigerant back into the compression chambers upon shutdown. This limits the amount of trapped gas communicating with the compression chambers, and greatly reduces the occurrence of reverse rotation.
The prior art valves have used large valve plates which are cast or otherwise formed to have a relatively thick configuration. These members are rigid, and do not have an easily deformed face which can adapt to the face of the valve seat and thus do not provide an ideal seal. Moreover, the structure provided for the prior art valve has included a stop between the rigid valve plate and a rigid separator plate, which is mounted directly below the valve. Upon start up of the compressor, the valve plate is quickly driven to its stop position, since there is no spring bias. Thus, the prior art rigid and relatively thick valve plate is driven to a position where it hits the rigid separator plate. This occurrence may sometimes cause damage to the valve plate, and thus is undesirable.
This type prior art valve 10 is shown in FIG. 1. As shown, a valve seat 11 includes a resilient clip 12 which snaps over a rear portion of the valve seat 11. A relatively thick cast valve plate 13 includes a sealing portion 14, and ears 15 at each side. A stop portion 16 is formed rearwardly of the ears 15. Clip 12 holds the valve plate 13 onto the valve seat 11. The closure portion 14 of the valve plate 13 selectively closes the fluid opening 17.
As shown in FIG. 2, when the compressor is shut down, the valve plate 13 is in the position shown in phantom at 14c. At this position, the port 17 is closed. Due to the rigid valve plate, a tight seal is not necessarily maintained around the entire valve plate. That is, the valve plate cannot easily adapt to the shape of the valve seat.
At start up, the valve plate 13 is driven rearwardly to the position shown in solid line. At this position, the stop portion 16 contacts and abuts a top surface 18 of a separator plate. When driven to this position, there are undesirably high impact forces between the stop portion 16 and the separator plate 18. These forces could cause damage to the valve plate 13.